The present invention lies in the field of metal cation chelators (ligands) and their use for purposes of decreasing the bioavailability of elements of the first transition series, and/or the removal from the body of these elements or those with similar chemical properties. First transition series elements are components of enzymes required for nucleic acid replication as well as general cell replication. By inhibiting nucleic acid replication these agents are useful in inhibiting growth of DNA and RNA viruses. By inhibiting bacterial and fungal cell replication these agents are useful in vitro as preservatives, and employing topical or systemic in vivo administration they are useful in treating bacterial and fungal infections and in wound care. By inhibiting protozoan cell replication these agents are useful in treatment of protozoan infections. By inhibiting mammalian cell replication, these agents are useful in treating neoplastic disease, in suppression of the immune response, in inhibition of osteoclast activity, and in termination of pregnancy. Iron, a first transition element, is involved in free radical mediated tissue damage. By decreasing the body free iron content, these agents inhibit free radical mediated tissue damage. Excess of body iron characterizes hemochromatosis/-hemosiderosis, and excess of the first transition series element, copper, characterizes Wilson""s disease. By removing either excess iron or copper from the body these agents are useful in treating these diseases. When combined with elements possessing paramagnetic properties, the chelating agents described herein also find diagnostic utility as contrast enhancing agents in magnetic resonance imaging. When combined with radioactive elements, these chelating agents find utility in nuclear medical imaging.
Metal cations belonging to the first transition series are known to play important coenzymatic roles in metabolism. Zinc is known to be a coenzyme for over eighty different enzyme systems including those directly involved with DNA and RNA synthesis such as thymidine kinase, DNA and RNA polymerases, reverse transcriptase and terminal deoxynucleotide transferase. Among its other coenzyme functions, iron is the coenzyme for myoglobin, the cytochromes and catalases and is thus essential for oxidative metabolism. Manganese and copper also play significant coenzyme roles, and other metal cations in the first transition series are considered to be essential trace elements although their metabolic role is less well defined.
Compounds capable of forming complexes with metal cations, which compounds are commonly referred to as chelators or ligands, are known to have a variety of uses in medicine. These include their use as pharmaceuticals in treating heavy metal poisoning, in treating diseases associated with trace metal excess such as iron storage and copper storage diseases (hemosiderosis and Wilson""s disease, respectively), as radiopharmaceutical agents in nuclear medical imaging when forming complexes with radioactive metals, as contrast enhancement agents in magnetic resonance imaging (MRI) when forming complexes with paramagnetic metals, and as contrast enhancement agents in radiography when forming complexes with heavy metals.
Examples of ligands employed in treating heavy metal poisoning such as that due to lead, mercury, and other metals, are ethylenediamine tetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA). The ligand desferrioxamine is used in treating iron storage disease, and the ligand penicillamine is used in the mobilization of copper in the treatment of Wilson""s disease.
Examples of complexes used to form radiopharmaceuticals useful in evaluations of the kidneys, bone and liver are complexes of technetium-99m (99mTc) with diethylenetriamine pentaacetic acid (DTPA), dimercaptosuccinic acid (DMSA), methylene diphosphonate (MDP) and derivatives of iminodiacetic acid (IDA).
Complexes of paramagnetic metal cations which are useful as MRI contrast agents operate by accelerating proton relaxation rates. Most commonly a metal cation, such as gadolinium (III), having a large number of unpaired electrons is complexed by a ligand suitable for complexation of that cation. An example is gadolinium (III) complexed by DTPA.
Chelators with affinity for iron cations have been shown to inhibit cell proliferation. Desferrioxamine is one example of such a chelator. This effect is thought to be a consequence of the complexation of tissue iron by the chelator, which thereby deprives the proliferating cells of a source of iron for critical enzyme synthesis. Moreover, it is believed that certain types of tissue damage are mediated by the formation of free radicals. It is also appreciated that catalytically active iron catalyzes formation of the highly active hydroxyl free radical. Based on such relationships chelators (ligands) for iron such as desferrioxamine and the experimental iron chelator xe2x80x9cL1xe2x80x9d (1,2-dimethyl-3-hydroxypyrid-4-one) have been examined in management of conditions where free radical mediated tissue damage is believed to play a role, as well as in clinical management of conditions in which control of cell proliferation is desired. Conditions where the administration of iron chelators has been evaluated include: rheumatoid arthritis, anthracycline cardiac poisoning, reperfusion injury, solid tumors, hematologic cancers, malaria, renal failure, Alzheimer""s disease, myelofibrosis, multiple sclerosis, drug-induced lung injury, graft versus host disease, and transplant rejection and preservation (Voest, E. E., et al., xe2x80x9cIron Chelating Agents in Non-Iron Overload conditions,xe2x80x9d Annals of Internal Medicine 120(6): 490-499 (Mar. 15, 1994)).
Agents which inhibit cell replication have found use in the prior art as chemotherapeutic agents for treatment of neoplasia and infectious disease, for suppression of the immune response, and for termination of pregnancy. Such agents usually act by inhibiting DNA, RNA or protein synthesis. This results in a greater adverse effect on rapidly proliferating cell populations than on cells xe2x80x9crestingxe2x80x9d in interphase or proliferating less rapidly.
Such agents may possess a degree of selectivity in treating the rapidly proliferating offending cell population, particularly in the case of certain neoplasias and infectious processes. These agents also inhibit replication of normal cells of the host organism, to varying degrees. Cells of the immune system proliferating in response to antigenic challenge are sensitive to such agents, and accordingly these agents are useful in suppressing the immunological response. Examples are the suppression of the homograft rejection response following tissue transplantation and the treatment of autoimmune disorders. Replication of protozoan, bacterial and mycotic microorganisms are also sensitive to such agents, which makes the agents useful in treating infections by such microorganisms.
Agents which suppress cell replication by inhibiting DNA or RNA synthesis have primarily found utility in treatment of neoplastic diseases. The glutamine antagonists azaserine, DON, and the anti-purines such as 6-mercaptopurine and 6-thioguanine principally inhibit DNA synthesis by their action on phosphoribosylpyrophosphate amidotransferase, the enzyme involved in the first step in purine nucleotide synthesis. The folic acid antagonists aminopterin arid methotrexate inhibit DNA synthesis (and other synthetic processes involving one carbon transport) by inhibiting the dihydrofolate reductase enzyme system, thereby interfering with formation of tetrahydrofolate, which is necessary in transfer of one-carbon fragments to purine and pyrimidine rings. Hydroxyurea inhibits DNA synthesis by inhibiting ribonuclease reductase, thereby preventing reduction of ribonucleotides to their corresponding deoxyribonucleotides. The anti-pyrimidines such as 5-fluorouracil inhibit DNA synthesis by inhibiting thymidylate synthetase. 5-Fluorouracil may also be incorporated into fraudulent RNA molecules. Bleomycin appears to inhibit DNA synthesis by blocking thymidine incorporation into DNA, although it may have other mechanisms of action. Agents such as 5-bromouracil and iododeoxyuridine may be incorporated into DNA in place of thymidine, and cytosine arabinoside may be incorporated into DNA in place of 2xe2x80x2-deoxycytidine. The fraudulent DNA produced by these incorporations interferes with the information transmittal system for DNAxe2x86x92RNAxe2x86x92protein synthesis.
Alkylating agents used in treating neoplasias, such as the nitrogen mustards, ethylene imines, alkyl sulphonates and antibiotics such as mitomycin C, suppress cell replication by attacking DNA and forming covalent alkylate linkages within preformed DNA, thereby interfering with DNA function and replication. The activity of such agents is therefore not limited to inhibition of cell replication alone.
Agents used in treatment of neoplasias such as 8-azaguanidine and 5-fluorouracil inhibit cell replication by being incorporated into fraudulent RNA. Agents such as actinomycin D, daunorubicin, nogalomycin, mithramycin and adriamycin are thought to inhibit RNA polymerase by strongly binding to DNA and thereby inhibiting DNA to RNA transcription.
Certain agents which inhibit cell replication by arresting metaphase (examples of such agents are colchicine, vinblastine, vincristine, podophyllotoxin, and griseofulvin) or arresting telophase (cytochalasins) have also been shown to be active in treating neoplasias or microbial infections.
Agents which inhibit cell replication primarily by inhibition of protein synthesis have found utility in the treatment of microbial infections. The tetracyclines, streptomycins and neomycin, for example, inhibit protein synthesis by inhibition of the mRNA-ribosome-tRNA complex. Chloramphenicol, erythromycin, lincomycin, puromycin appear to inhibit protein synthesis by inhibition of the peptidyl synthetase reaction. A miscellaneous group of antibiotics appear to act by inhibition of translocation of the ribosome along mRNA. Penicillins act by inhibiting synthesis of the bacterial cell wall.
Complexes of heavy metals such as platinum have been found to be active in treatment of certain neoplasias. The inhibition of cell replication by these complexes is attributed to the in vivo hydrolysis of one or more of the coordinating ligand sites occupying positions in the coordination shell of the metal. This hydrolysis liberates the coordination sites for in vivo interaction with nucleophilic donor sites which are critical to replication or survival of the cell population. There is a wide diversity of such donor sites in vivo, but it is believed that one critical set of donor sites involves binding of the platinum to two guanine or one guanine and one adenine residue of opposing strands of DNA.
The mechanisms of action of the various agents employed in treating protozoan infection are largely unknown. However, it has been demonstrated that agents which interfere with cell replication can be active in treating such infections. For example, the antimalarial agent chloroguanide and the diaminopyrimidines act as selective inhibitors of plasmodial dihydrofolate reductase thereby inhibiting plasmodial DNA replication. Tetracyclines possess antimalarial and antiprotozoal activities possibly acting by mechanisms similar to those operative in their inhibition of bacterial replication. The antibiotics puromycin and erythromycin, as well as tetracyclines which inhibit microbial replication, have also been employed in treatment of amebiasis. The antiprotozoal effects of the diamidines is believed to be due to their inhibition of cell replication by interference with DNA.
Based on what is known from the action of the agents cited above, one can readily conclude that agents which inhibit cell replication, regardless of the specific biochemical mechanism involved, have utility in the treatment of a wide variety of neoplastic and infectious diseases and in the management of certain of the body""s responses which are mediated through selective in vivo cell replication.
The present invention resides in the discovery that a class of substituted polyaza compounds showing affinity and selectivity for first transition series elements (atomic numbers 21-30) are capable of inhibiting cell proliferation of mammalian, bacterial and yeast (fungal) cell populations and are therefore useful in vitro as preservatives and in vivo, administered topically or parenterally, in treatment of a wide variety of conditions including neoplasia, infection, inflammation, wound care, suppression of the immune response, inhibition of osteoclasts in treatment of osteoporosis and in termination of pregnancy. It is believed that the mechanism for inhibition of cell proliferation by these compounds lies in their ability to decrease the bioavailability of essential first transition series elements. The term xe2x80x9cdecrease the bioavailabilityxe2x80x9d is used herein to denote a reduction or elimination of the accessibility of these elements to biological systems and thereby a reduction or elimination of the ability of these elements to perform the functions they would otherwise perform in living systems. Since these compounds decrease the bioavailability of zinc and iron, they are useful in inhibiting replication of DNA and RNA viruses. Since these compounds decrease the in vivo availability of tissue iron, they are also useful in management of free radical-mediated tissue damage and oxidation-mediated tissue damage. The compounds can also be prepared as complexes with radioisotopic or paramagnetic cations of first transition series elements, or with elements having chemical properties similar to those of first transition series elements. Complexes prepared in this manner are useful as diagnostic agents in nuclear medicine and magnetic resonance imaging.
By virtue of their affinity and selectivity, these substituted polyaza compounds are effective in treating diseases characterized by excess of first transition series elements, such as hemosiderosis (iron) and Wilson""s disease (copper).
For therapeutic purposes these agents may be employed in their free ligand form or in a protected form (for example, as the ester of the pendant donor, group) where the protecting group can be removed in vivo by enzymatic action to release the active ligand form. The agents can be administered as either the free chelator, as a protected form of the chelator, or as physiological salts of these forms. Physiologically and pharmacologically acceptable salts of these compounds dissolved in suitable vehicles are fully suitable for use as pharmaceutical agents.
These compounds of this invention are chemically distinct from previously known antibiotic and chemotherapeutic agents which affect cell proliferation and which might also possess some properties as metal ion ligands. Unlike the chemotherapeutic complexes between a ligand and a heavy metal cation (such as platinum, for example) in which the complexed heavy metal provides the basis for the therapeutic effect and the purpose of the ligand portion of the complex is related to the in vivo distribution and hydrolysis rates of the complex, the compounds of this invention are active in the form of the metal-free ligand and do not require the addition of a heavy metal to exercise their therapeutic effect. The compounds of the invention are also chemically distinct from agents previously employed clinically as chelators of certain first transition series elements (such as desferrioxamine and 1,2-dimethyl-3-hydroxypyrid-4-one for chelation of iron, and penicillamine for chelation of copper).
Subclasses of compounds of this invention are novel compounds, structurally distinct from previously disclosed chelators and any complexes derived therefrom. Complexes of these subclasses in combination with radioisotopes or paramagnetic cations are particularly useful in diagnostic studies in nuclear medicine or in magnetic resonance imaging, respectively.
Abbreviations
Abbreviations are used herein, in conformance with standard chemical practice, as follows: Bz, benzyl; Me, methyl; Et, ethyl; Pr, propyl; iPr, isopropyl; iBu, isobutyl; Bu, butyl; tBu, tertiary-butyl; Ts, para-toluenesulfonyl; Tfxe2x88x92, trifluoroacetate; DMSO, dimethylsulfoxide; DMF, dimethylformamide; DEK, diethyl ketone (3-pentanone); MeOH, methanol; LDA, lithium diisopropylamide; THF, tetrahydrofuran; Py, pyridine; Ac, acetyl; Ac2O, acetic anhydride
The present invention provides methods of in vitro and in vivo complexing of first transition series element cations. The invention further provides methods of treating conditions dependent on the bioavailability of first transition series elements and also conditions associated with elevated levels of first transition series elements. Diagnostic methods are also provided which are useful in nuclear medicine and magnetic resonance imaging. The in vivo methods involve administering to a patient or host, a chelating agent (or ligand) which is capable of complexing first transition series elements as well as elements with chemical characteristics similar to those of first transition series elements. For the diagnostic methods, the chelating agent is administered as a complex of radioisotopic or paramagnetic cations of first transition series elements (or those with similar properties).
Among the ligands used in the practice of the present invention are the embodiments represented by the following formulas: 
In Formulas I through IV, R1, R2, R3, and R4 may be the same or different on any single molecule, and the same is true for R11, R12, and R13, for R21, R22, and R23, and for R31, R32, and R33. Each of these symbols (R1 through R33) represents H, alkyl, alkenyl, aryl, arylalkyl, alkoxy, alkylthio, alkenoxy, alkenylthio, aryloxy, arylthio, alkyl interrupted by one or more oxa (xe2x80x94Oxe2x80x94), alkenyl interrupted by one or more oxa (xe2x80x94Oxe2x80x94), alkyl interrupted by thia (xe2x80x94Sxe2x80x94), alkenyl interrupted by thia (xe2x80x94Sxe2x80x94), aryloxyalkyl, alkoxyaryl, aminoalkyl, aminoalkenyl, aminoaryl, aminoarylalkyl, hydroxyalkyl, hydroxyalkenyl, hydroxyaryl, or hydroxyarylalkyl, provided only that these groups do not interfere with complexation and they are not combined in a manner which results in a chemically unstable configuration. The alkyl, alkenyl and aryl groups, or portions of groups, in the foregoing list can also be substituted with one or more halogen atoms.
In addition to the radicals and radical subclasses listed above, R1, R4, R11, R21 and R31 are further defined to include: 
In Formula V, R41, R42, and R43 may be the same or different on any single radical, and are defined as H, alkyl, alkenyl, aryl, arylalkyl, alkoxy, alkylthio, alkenoxy, alkenylthio, aryloxy, arylthio, alkyl interrupted by oxa (xe2x80x94Oxe2x80x94), alkenyl interrupted by oxa (xe2x80x94Oxe2x80x94), alkyl interrupted by thia (xe2x80x94Sxe2x80x94), alkenyl interrupted by thia (xe2x80x94Sxe2x80x94), aryloxyalkyl, alkoxyaryl, aminoalkyl, aminoalkenyl, aminoaryl, aminoarylalkyl, hydroxyalkyl, hydroxyalkenyl, hydroxyaryl, or hydroxyarylalkyl, provided only that these groups do not interfere with complexation and that they are not combined in a manner which results in a chemically unstable configuration. Here as well, the alkyl, alkenyl and aryl groups, or portions of groups, in the list can be substituted with one or more halogen atoms. R44 in Formula V is defined as H, hydroxy, amino, alkyl, alkyl interrupted by oxa (xe2x80x94Oxe2x80x94), alkoxy, aryl, aryloxyalkyl, alkoxyaryl, or any of these groups in which the alkyl and aryl portions are substituted with one or more halogen atoms. Again, the groups are selected such that they do not interfere with complexation and are not combined in a manner which results in a chemically unstable configuration.
The index n is either zero or 1.
The symbol X represents any of the following groups: 
In these formulas, R41, R42, R43, and R44 may be the same or different on any single radical, and have the same definitions as R41, R42, and R43 given above.
R46, R47, R48 and R49 may be the same or different on any single radical, and are each defined as H, or alkyl or aryl groups which do not interfere with complexation. R46 and R47 may further be combined as a single divalent group, thereby forming a ring structure. R48 and R49 are further defined to include alkoxy, alkyl interrupted by oxa (xe2x80x94Oxe2x80x94), aryloxyalkyl, and alkoxyaryl, combined in a manner which results in a chemically stable configuration. All alkyl and aryl groups in this paragraph, including alkyl and aryl portions of groups, are optionally substituted with one or more halogen atoms.
R50, R51 and R52 may be the same or different on any single radical, and are each defined as H, alkyl, alkenyl, aryl, arylalkyl, alkyloxy, alkylthio, alkenyloxy, alkenylthio, aryloxy, arylthio, aminoalkyl, aminoalkenyl, aminoaryl, aminoarylalkyl, hydroxyalkyl, hydroxyalkenyl, hydroxyaryl, or hydroxyarylalkyl.
The index m is an integer which is either 1, 2 or 3.
Returning to Formulas I through IV, further variations within the scope of this invention are as follows:
(1) Internal cyclizations within these formulas at the nitrogen atoms, formed by joining together any two of the R1 and R2 groups in Formula I, any two of the R11 groups in Formula II, any two of the R21 groups in Formula III, or any two of the R31 groups in Formula IV, as a single divalent group bridging the two nitrogen atoms, the single divalent group having the formula 
xe2x80x83in which R2 and R3 are as defined above, and s is at least 2, preferably 2 or 3;
(2) Dimers or other two-molecule combinations of Formulas I through IV (the molecules being the same or different), formed by bridging the molecules together through one or more divalent groups of Formula VI (as defined above) substituted for any one or two of the R11 groups in Formula II, any one or two of the R21 groups in Formula III, or any one or two of the R31 groups in Formula IV;
(3) Internal cyclizations at common carbon atoms within these formulas to form homocyclic rings, by joining one or more of the R2, R12, R22, or R32 groups to one or more of the R3, R 13, R23, or R33 groups at the same carbon atom, as a single divalent group of Formula VI (as defined above), and forming one or more such homocyclic rings per structure in this manner; and
(4) Internal cyclizations involving two carbon atoms separated by a nitrogen atom within these formulas to form heterocyclic rings, by joining any two adjacent R2 groups in Formula I, any two adjacent R12 groups in Formula II, any two adjacent R22 groups in Formula III, or any two adjacent R32 groups in Formula IV, as a single divalent group of Formula VI (as defined above), and forming one or more such heterocyclic rings per structure in this manner.
In Formula I, the subscripts p and q may be the same or different, and are each either 2 or 3. The subscript r is 0 to 4 inclusive, preferably 1 to 2 inclusive.
In Formula II, t, u and v may be the same or different, and are each either 2 or 3. The value of w is at least 1, more preferably 1 to 4 inclusive, still more preferably 1 to 3 inclusive, and most preferably either 1 or 2.
The terms used in connection with these formulas have the same meaning here as they have in the chemical industry among those skilled in the art. The term xe2x80x9calkylxe2x80x9d thus encompasses both straight-chain and branched-chain groups and includes both linear and cyclic groups. The term xe2x80x9calkenylxe2x80x9d refers to unsaturated groups with one or more double bonds and includes both linear and cyclic groups. The term xe2x80x9carylxe2x80x9d refers to aromatic groups of one or more cycles.
For all such groups, those which are useful in the present invention are those which do not impair or interfere with the formation of chelate complexes. Within this limitation, however, the groups may vary widely in size and configuration. Preferred alkyl groups are those having 1 to 8 carbon atoms, with 1 to 4 carbon atoms more preferred. Prime examples are methyl, ethyl, isopropyl, n-butyl and tert-butyl. Preferred aryl groups are phenyl and naphthyl, particularly phenyl. Preferred aryl alkyl groups are phenylethyl and benzyl, and of these benzyl is the most preferred. Preferred cycloalkyl groups are those with 4 to 7 carbon atoms in the cycle, with cycles of 5 or 6 carbon atoms particularly preferred. Preferred halogen atoms are chlorine and fluorine, with fluorine particularly preferred.
One particularly preferred subclass of compounds within Formula I are those in which R1 is alkyl, alkenyl, aryl, arylalkyl, or cycloalkyl, substituted at the xcex2-position with hydroxy. Likewise, R11 in Formula II, R21 in Formula III, and R31 in Formula IV are each preferably alkyl, alkenyl, aryl, arylalkyl, or cycloalkyl, substituted at the xcex2-position with hydroxy. Further preferred are compounds in which one or more, and preferably two or more, of such groups (R1, R11, R21 and R31 on the same formula are substituted at the xcex2-position with hydroxy. Still further preferred are compounds in which the xcex2-hydroxy substituted groups are further substituted at the xcex2-position with at least one hydroxymethyl, alkoxymethyl, alkenoxymethyl, aryloxymethyl, or combinations thereof, all of which may also be further substituted with halogen. Included among these are compounds are compounds of Formula III in which one or more of the R21 groups are substituted at the xcex2-position with hydroxy and also with hydroxymethyl, alkoxymethyl, alkenoxymethyl, or aryloxymethyl, all of which may also be further substituted with halogen, and the R22 and R23 groups are all hydrogen atoms.
Certain specific groups for R1, R11, R21, and R31 are particularly preferred. These are: 2-hydroxy(2,2-diisopropoxymethyl)ethyl and (3-hydroxy-6,6,7,7-tetramethyl-1,5-dioxacyclohept-3-yl)methyl.
For use in the present inventive methods, the complexes will preferably have a molecular weight which does not exceed 2000. More preferably the complexes will have molecular weights of from 200 to 1800, still more preferably of from 400 to 1100.
Among the complexes used in the practice of the present invention are the embodiments represented by the complexes formed between the ligands described above and paramagnetic metal cations or radioisotopic metal cations. These paramagnetic metal cations include elements of atomic numbers 22 through 29 (inclusive), 42, 44 and 58 through 70 (inclusive). Of these, the ones having atomic numbers 22 through 29 (inclusive) and 58 through 70 (inclusive) are preferred, and those having atomic numbers 24 through 29 (inclusive) and 64 through 68 (inclusive) are most preferred. Examples of such metals are chromium (III), manganese (II), iron (II), iron (III), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), gadolinium (III), terbium (III), dysprosium (III), holmium (III), erbium (III) and ytterbium (III). Chromium (III), manganese (II), iron (III) and gadolinium (III) are particularly preferred, with gadolinium (III) the most preferred.
Some methods of the present invention will use radioisotopic labels which will facilitate imaging of various disease states including tumors, inflamed joints or lesions or suspected lesions. The use of gamma emitting radioisotopes is particularly advantageous as they can easily be counted in a scintillation well counter, do not require tissue homogenization prior to counting, and can be imaged with gamma cameras.
Gamma or positron emitting radioisotopes are typically used in accordance with well known techniques. Suitable gamma-emitting radioisotopes include 99Tc, 51Cr, 59Fe, 67Ga, 86Rb, 111In and 195Pt. Suitable positron-emitters include 68Ga.
Where indicated, physiologically or pharmacologically compatible salts of the ligands, or complexes thereof, which have an excess of acidic groups are formed by neutralizing the acidic moieties of the ligand with physiologically or pharmacologically compatible cations from corresponding inorganic and organic bases and amino acids. Examples are alkali and alkaline earth metal cations, notably sodium. Further examples are primary, secondary and tertiary amines, notably, ethanolamine, diethanolamine, morpholine, glucamine, N,N-dimethylglucamine, and N-methylglucamine (commonly referred to as xe2x80x9cmegluminexe2x80x9d). Examples of amino acid cations are lysines, arginines and ornithines.
Similarly, physiologically and pharmacologically compatible salts of those ligands which have an excess of basic groups are formed by neutralizing the basic moieties of the ligand with physiologically or pharmacologically compatible anions from corresponding inorganic and organic acids. Examples are halide anions, notably chloride. Further examples are sulfates, bicarbonate, acetate, pyruvate and other inorganic and organic acids.
Pharmaceutical compositions comprising the chelates described herein are prepared and administered according to standard techniques. The pharmaceutical compositions can be administered parenterally, i.e., intraarticularly, intravenously, subcutaneously, or intramuscularly. Suitable formulations for use in the present invention are found in Remington""s Pharmaceutical Sciences, Mack Publishing Company, Philadelphia, Pa., 17th ed. (1985).
The chelate compositions can be administered intravenously. Thus, this invention provides compositions for intravenous administration which comprise a solution of the chelate suspended in an acceptable carrier, preferably an aqueous carrier. A variety of aqueous carriers may be used, e.g., water, buffered water, 0.9% isotonic saline, and the like. These compositions may be sterilized by conventional, well known sterilization techniques, or may be sterile filtered. The resulting aqueous solutions may be packaged for use as is, or lyophilized, the lyophilized preparation being combined with a sterile aqueous solution prior to administration. The compositions may contain pharmaceutically acceptable auxiliary substances as required to approximate physiological conditions, such as pH adjusting and buffering agents, tonicity adjusting agents, wetting agents and the like, for example, sodium acetate, sodium lactate, sodium chloride, calcium chloride, sorbitan monolaurate, triethanolamine oleate, etc.
The concentration of chelates, in the pharmaceutical formulations can vary widely, i.e., from less than about 0.05%, usually at or at least about 2-5% to as much as 10 to 30% by weight and will be selected primarily by fluid volumes, viscosities, etc., in accordance with the particular mode of administration selected. For diagnosis, the amount of chelates in administered complexes will depend upon the particular metal cation being used and the judgement of the clinician. For use in magnetic resonance imaging the dose typically is between 0.05 to 0.5 millimoles/kg body weight.
In general, any conventional method for visualizing diagnostic imaging can be used, depending upon the label used. Usually gamma and positron emitting radioisotopes are used for imaging in nuclear medicine and paramagnetic metal cations are used in magnetic resonance imaging.
The methods of the present invention may be practiced in a variety of hosts. Preferred hosts include mammalian species, such as humans, non-human primates, dogs, cats, cattle, horses, sheep, and the like.